1. Field of the Invention
The present invention relates to a braking device in a vehicle.
2. Background Art
A conventional braking operation in a motorcycle is carried out by operating a brake lever provided on a handle grip, and a brake pedal provided on a step. An electronic control is applied to a part of the brake system to control a front brake for braking a front wheel, and a rear brake for braking a rear wheel. Such a brake system employing electronic control is described in Japanese Patent Laid-open No. 7-196068.
In Japanese Patent Laid-open No. 7-196068, an operational pressure generated in a primary master cylinder operated by the brake lever or the brake pedal is detected, and an electronic control unit controls an actuator according to the operational pressure detected. An output from the actuator and the output from the primary master cylinder are separately input into a secondary master cylinder, and a hydraulic pressure generated in the secondary master cylinder is supplied through a control valve to the brake.
The above brake system is limited in that the operational input from an operator and the input from the electronic control unit interfere with one another.
To avoid such interference, it is possible to configure two independent input systems for independently applying the operational input from the operator, and the input from the electronic control unit to the brake. However, if an anti-skid brake system ("ABS") is added to the system, control logic is complicated because the two systems are controlled independently of each other. The number of parts and the cost is thereby increased.
FIG. 10 of the present application shows another conventional brake system. In FIG. 10 of the present application, reference numerals 02 and 05 denote front and rear hydraulic brakes, respectively. Reference numerals 06 and 011 denote a brake lever and a brake pedal, respectively, as brake operating means. The brake lever 06 is provided with a lever master cylinder 07, and the brake pedal 011 is provided with a pedal master cylinder 012.
A lever hydraulic system 08 extending from the lever master cylinder 07 is connected to the front brake 02. A pedal hydraulic system 013 extending from the pedal master cylinder 012 is connected to one of the three ports of the rear brake 05. A hydraulic circuit 014 branched from the pedal hydraulic system 013 is connected to a secondary master cylinder 010. An output from the secondary master cylinder 010 is connected through a control valve 016 to the other two ports of the rear brake 05.
The brake lever 06 is provided with a brake switch 040 adapted to open and close according to whether the brake lever 06 is pivotally moved. The lever hydraulic system 08 is provided with a pressure sensor 041 for detecting a hydraulic pressure generated in the lever master cylinder 07. Detection signals from the brake switch 040 and the pressure sensor 041 are input into a control unit 031. The control unit 031 decides a hydraulic pressure to be generated in the secondary master cylinder 010 according to the detection signals from the brake switch 040 and the pressure sensor 041, and operates an actuator 033 through a relay 032 to thereby generate the decided hydraulic pressure in the secondary master cylinder 010. In the case that the brake pedal 011 only is operated, only the rear brake 05 is operated.
In the case that the brake lever 06 only is operated or both the brake lever 06 and the brake pedal 011 are simultaneously operated, the hydraulic pressure generated in the lever master cylinder 07 operates the front brake 02. At the same time, the actuator 033 is operated by the control unit 031 according to the hydraulic pressure in the lever hydraulic system 08 to generate a required hydraulic pressure in the secondary master cylinder 010. This hydraulic pressure operates the rear brake 05 through the control valve 016.
The output from the electronically controlled actuator 033 interferes with the pedal hydraulic pressure in the secondary master cylinder 010, and is thereafter mechanically set by the control valve 016. As a result, the degree of freedom of electronic control is limited.
In this manner, the electronically controlled brake system connected to the two ports of the brake caliper of the rear brake 05 is not completely independent of the pedal hydraulic system, but is affected by the pedal hydraulic pressure. Accordingly, it is difficult to electronically give priority to the pedal operation by an operator to perform brake control. As a result, braking operability by the operator is limited.
It is accordingly an object of the present invention to provide a braking device in a vehicle which can increase the degree of freedom of electronic control by making an independent electronically controlled brake system act on a part of a hydraulic brake, and which can also ensure braking operability by an operator.
It is also an object of the present invention to provide a braking device in a vehicle having ABS control means which can eliminate interference between inputs, and avoid overly complicated control logic.